Data Preprocessing in Tableau

In previous article, I created two tables in my Redshift Cluster. Now I wan’t to find out the relation between salary of every employee and their working age. Tableau is the best choice for visualizing data analysis (SAS is too expensive and has no trail-version for learning).
First, we connect to Redshift in Tableau, and double-click the “New Custom SQL”. In the popup window, type in our SQL to query first-year-salary of every employee:

Now we have the table “custom sql query”. Drag in table “salary”, and choose “inner join” for employee_id, start_date:

Click into the “Sheet 1”. Drag “salary” to “Rows”, “min_start_date” to “Columns”, and “employee_id” to “Color” in “Marks” panel.

Now we can see the “expensive employees” (who have the most high salary in the same first-year) on the top of the graph:

Instead of adding custom SQL in tableau datasource panel, we can also create view in Redshift, and let tableau show views in “Tables”.